This ticket is to upgrade to Giac 1.5.

A preliminary version "1.5.0 unstable" is available for testing:

• announcement on Giac / Xcas forum
• source tarball for giac-1.5 (take latest giac-1.5.x-y).
• README about source tarballs for Giac and their version numbering

This upgrade should solve #25822 and #25324 since the issues reported there are fixed upstream.

All that will be left to do in those tickets is add doctests.

I suppose we finally have stable 1.5.0, here
(repacked):
tarball: http://users.ox.ac.uk/~coml0531/sage/giac-1.5.0.37.tar.bz2

CC: @antonio-rojas @kiwifb @frederichan-IMJPRG @infinity0 @saraedum @tobihan @timokau

Component: packages: standard

Keywords: upgrade, giac

Author: Dima Pasechnik

Branch: 5986d80

Reviewer: François Bissey, Jeroen Demeyer

Issue created by migration from https://trac.sagemath.org/ticket/26315